A blog on DNA evidence

There But for the Grace of God … The “Horrific False-positive DNA Match” to Diane Myers

I have been trying to make sense of a 2004 newspaper report [1] that has achieved a certain degree of fame in articles and briefs emphasizing the risks of false accusations or convictions resulting from cold hits in DNA databases. The article appeared in November 2004, in the Chicago Sun-Times, with no follow-up in that paper or, as far I can see, in any other. In 2009, the Federal Public Defender in Sacramento cited it as an example of “horrific tales of false-positive DNA matches” [2, at 17].

In this tale, detectives investigating a string of burglaries “were informed of a ‘hit’ between blood recovered at the scene and the genetic profile of a woman named Diane Myers.” [1] Evidently, they were not informed that “the ‘hit’ was not based on a direct match.” It was some kind of “partial match” provided as an “investigative lead.” The article does not explain further. One of the reporters responded to a recent email that she does not recall the details. The suspect promptly cleared herself by showing that “she was locked up in a Downstate prison [when someone] slipped into the Chicago apartment Dec. 12, 2002.” [1]

What might have happened had she not been so lucky as to have an airtight alibi? “Jack Rimland, a criminal defense attorney and former president of the Illinois Association of Criminal Defense Lawyers, said … ‘But for the fact that this woman was in prison [sic] … I absolutely believe she’d still be in custody.'” On the other hand, “Kathleen Zellner, a Naperville attorney who relied on DNA evidence to exonerate four men in the 1986 killing of medical student Lori Roscetti, said it was ‘reassuring’ the error was in paperwork, and not in the scientific process, and that the mistake appears to have been addressed.” [1]

All told, this incident does not seem to me to merit the appellation of “horrific,” but it does illustrate the need for the police to understand the true significance of every cold hit. When only a few loci are involved, the power of the association obviously is reduced. If anyone knows more about the laboratory report in the case, the probability of a random match for the limited number of loci involved, and how reports of database hits have changed in Illinois, please consider posting a comment or emailing me.